Problem: If $6a + 9b = -7$ and $7x + 6y + 7z = 7$, what is $-42a - 63b - 12y - 14z - 14x$ ?
Solution: $= -42a - 63b - 14x - 12y - 14z$ $= (-7) \cdot (6a + 9b) + (-2) \cdot (7x + 6y + 7z)$ $= (-7) \cdot (-7) + (-2) \cdot (7)$ $= 49 - 14$ $= 35$